The dissociation of mineral monomers is one of the key factors that can be efficiently sorted. The crushing method has a great influence on the dissociation degree of mineral monomers. The Bayan Obo rare earth mine contains more than a dozen rare earth minerals, with the close symbiosis of minerals and complex embedded types. Among them, the rare earth is mainly concentrated in bastnaesite and monazite ore. The analysis shows that minerals form contiguous, network veins, dissolution and ring embedment due to mutual enveloping, interpenetrating and alternation. To improve the dissociation degree of mineral monomers, the water jet mineral dissociation device was independently developed to explore the influence of water jet velocity on the dissociation degree of rare earth monomers in Bayan Obo Mine. Under the same particle size distribution, the experimental results of high-pressure water jet pulverization and conventional ball milling (iron medium) were compared, and the effects of the two pulverization methods on the dissociation state of rare earth minerals and the particle interface were analyzed. The analysis by laser confocal microscope and the automatic quantitative analysis system of mineral characteristics (AMICS) showed that the dissociation degree of the high-pressure water jet crushing Bayan Obo rare earth mineral monomer was better than that of ball milling, and it had the characteristics of high dissociation degree and relatively uniform particle size, the natural interface of mineral particles keep better, the surface was smoother, the rare earth minerals were concentrated in the particles below 0.038 mm, which was beneficial to the flotation separation of rare earth, and had certain guiding significance for the ore crushing of the Bayan Obo mine.